1. Field of the Invention
The present invention relates to a technique capable of lessening so-called color bleeding (phenomenon) which occurs upon the formation of color images on plain paper with inks and for providing images high in water fastness. In particular, this invention relates to a liquid composition suitable for use in the formation of images making good use of an ink-jet system. In addition, the invention includes an ink set comprising in combination this composition and at least one ink, and an image-forming process and apparatus to which these liquid composition and ink set are applied.
2. Related Background Art
An ink-jet recording method is a system in which recording is conducted by ejecting droplets of ink to apply them to a recording medium such as paper. In particular, according to the methods disclosed in Japanese Patent Publication Nos. 61-59911, 61-59912 and 61-59914, an electrothermal converter is used as an ejection-energy supply means to apply thermal energy to an ink so as to generate bubbles, thereby ejecting droplets of the ink. The formation of a high-density multi-orifice recording head can be realized with ease, and high-resolution and high-quality images can be recorded at high speed.
However, the conventional inks used in ink-jet recording generally comprise, as a principal component, water, and include additionally a water-soluble high boiling solvent such as glycol for the purpose of preventing drying and clogging at orifices, and the like. When such an ink has been used to conduct recording on plain paper, there exist problems that fixing ability cannot be sufficiently achieved, and image irregularity occurs, which appears to be attributed to the uneven distribution of the filler and size on the surface of the recording paper. In particular, when color images are intended to form, plural inks of different colors are overlapped one after another before they are fixed to paper. Therefore, color bleeding and uneven color mixing have occurred at portions of boundaries between images of different colors (this phenomenon will hereinafter be referred to as "bleeding" simply), resulting in a failure to obtain satisfactory images.
As a means for enhancing fixing ability of inks, Japanese Patent Application Laid-Open No. 55-65269 discloses the addition of a compound capable of enhancing penetrability, such as a surfactant, into the inks. Besides, Japanese Patent Application Laid-Open No. 55-66976 discloses the use of inks comprising, as a principal component, a volatile solvent. However, the former method, in which the compound capable of enhancing penetrability added into the inks, has involved a disadvantage that although the penetrability of the inks into recording paper is improved, and so the fixing ability and anti-bleeding property of the inks are improved to some extent, the image density and saturation of the resulting image are lowered because coloring materials contained in the inks also penetrate deeply into the recording paper. In addition, the inks also have the problem that they spread in lateral directions, resulting in reduction of edge sharpness and resolution. On the other hand, in the latter method, in which the inks comprising, as a principal component, the volatile solvent are used, clogging due to the evaporation of the solvent in a nozzle of a recording head occurs in addition to the above-described disadvantages of the former method. Such methods have hence not been preferred.
In order to improve the above-described problems, there have been further disclosed methods in which a liquid, which can make the quality of images better, is applied to a recording medium prior to the jetting of an ink.
For example, Japanese Patent Application Laid-Open No. 63-299971 discloses a method in which a liquid comprising an organic compound having two or more cationic groups per molecule is applied to a recording medium, and recording is then conducted with inks comprising an anionic dye. Japanese Patent Application Laid-Open No. 64-9279 discloses a method in which an acidic liquid containing succinic acid or the-like is applied to a recording medium, and recording is then conducted with inks comprising an anionic dye. Further, Japanese Patent Application Laid-Open Nos. 64-63185 discloses a method in which a liquid, which insolubilizes dyes, is applied to a recording medium prior to recording.
However, all these methods intend to prevent bleeding of images or improve the water fastness of images owing to the deposition of the dyes themselves in the inks. Therefore, these methods are still incapable of preventing the above-described bleeding between inks of different colors. More over, these methods suffer poor coverability of the inks on pulp fibers in the recording paper because the dyes deposited tend to distribute unevenly on the recording paper, resulting in reduction of evenness of images.